RE: [CAD_CAM_EDM_DRO] Re: Thoughts on PC Based Control Retrofit....now transformers.

Doug:

I think that you're referring to a multitapped transformer. The buck-boost
transformers that I've run into are typically a "standard" 120 Volt to 24
volt step down transformer (or 12 volt, etc.) The 120 volt input of this
transformer is run by a variac, so you can vary its input voltage. The
output of the transformer is put in series with the output of the isolation
transformer. Connected one way, the two voltages add and the output voltage
is the sum. Reverse the buck-boost leads and the buck-boost voltage is
subtracted from the isolation transformer output. If necessary, you can even
run the variac with a motor and actually measure and control the output
voltage. Some of the automatic regulators are commercially available as
well.Doug:D

-- Carol & Jerry Jankura
Strongsville, Ohio
So many toys, so little time



-----Original Message-----
From: Doug Harrison [mailto:prototype@...]
Sent: Friday, May 04, 2001 9:39 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: Thoughts on PC Based Control
Retrofit....now transformers.

> You don't have to import anything into the States. Most of the Electrical
> Supply Houses (GE Supply, Graybar - to name a few) stock these types of
> transformers. They typically have four windings on them. Each winding has
> the same rating. You connect two for the primary and two for the

secondary.

I have acquired several of these. The problem is that many (most) electric
companies run their lines on the high side. Incoming voltage at my shop
runs as high as 127V per leg. 2:1 step down results in about 63V. Subtract
a volt or two for the diodes and multiply that by the square root of two and
you get just a little more than the 80V limit for Geckodrives.

80V seems to be a common upper limit for drive voltage with many stepper and
servo amps.

The transformers you want to look for are called isolated buck/boost
transformers. You want the isolated kind, not autotransformers. B/B
transformers have a multi-tapped secondary, typically 90, 95, 100, 105 volts
output from a 220V input. At 120V in you will get at least one combination
that will be close enough to what you want. Just remember that a 2KVa
transformer is only good for half that amount at half it's rated input
voltage.

Doug


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